I’m starting a small series of “serious” articles, in order to show the different possibilities to stock hydrogen.
In this post, we’re going to see the different ways to stock hydrogen in liquid forms. Currently, 3 possibilities exist to stock hydrogen in liquid form: hydrogen liquefaction at cryogenic temperature, rooting out hydrogen from sodium borohydride solution (NaBH4) or hosting dyrdogen into organic liquid environment.
The liquid hydrogen temperature is very law : -250°C at atmospheric pressure, but in this state, its density reaches 71kg/m3 (against only 0.09kg at room temperature and so gaseous form!). So it permits to stock hydrogen at low pressure, but the liquefaction process is very expensive, and the storage is complicated. Indeed, a quotidian lost by evaporation of 1 or 2% occurs. It’s very useful in aero spatial areas, but not that convenient for car utilisation.
It’s also possible to stocks liquid sodium borohydride solution and to deliver hydrogen thanks to a simple chemical reaction involving water:
Thanks to water and a catalyst, hydrogen gas can be produced to feed a fuel cell, useful in car utilisation. In fact, this solution is stable and secure, and can contain until 10.9%w of hydrogen. The borate sodium (the reaction product NaBO2(s)) can be used to make soap or detergent.
The last possibility is to use naphthalene and benzene solutions, you can hydrogenate them at hugh temperature (100 until 150°C) to create 2 new stable molecules: cyclohexan and decalin. Those reaction products can be rehydrogenated for second utilisation. Unfortunately, those products are toxic and flammable so not that secure for car utilisation.
To conclude, the best way to store hydrogen in liquid form will depends of your utilisation, for a large scale use, you’ll prefer to use low cost and environment friendly elements, while for application requiring high concentration of power, cryogenic utilisation will be chosen.